Prostate cancer is the most common cancer in men. The majority of prostate cancer deaths are due to the development of metastatic disease that is unresponsive to conventional androgen deprivation therapy. Androgen deprivation therapy has been the standard of care in subjects with prostate cancer since the 1940s. Despite androgen deprivation, most subjects ultimately experience disease progression. For many years this later phase of the disease was called “hormone insensitive prostate cancer” or “androgen independent prostate cancer.” It has since become clear that the prostate cancer that emerges after years of androgen deprivation therapy remains dependent upon androgen. The prostate cancer cells that have survived have gained the ability to import low levels of circulating androgens (expressed from adrenal glands), become much more sensitive to these low levels of testosterone, and actually synthesize testosterone within the prostate cancer cell itself. This stage of prostate cancer is now termed “castration resistant prostate cancer” or CRPC.